JPH02270608A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent local wear of a shoulder rib by specifying a distance between a tire equator and a tread end, a distance between the tread end and a shoulder rib groove, a relation between the width and depth of the shoulder rib groove, and the other, respectively. CONSTITUTION:The relations of Rw/W=0.28 to 0.42, Rs/W=0.05 to 0.12 and Rd/W=0.07 to 0.19 hold, wherein W(mm) is a distance between a tire equator S and a tread end 28, Rw(mm) is a distance between the tread end 28 to a shoulder rib groove 24, Rs(mm) is a width of the shoulder rib groove 24 and Rd is a depth thereof. Further, a relation of -7 deg.<=alpha, beta<=7 deg. holds, wherein alpha, betaare respective angles formed by respecting facing side walls of the shoulder rib groove 24 and a line N rectangular to the surface of the tread portion 20. Thus, it is possible to effectively prevent local wear of the shoulder rib 26.

Description

Detailed Description of the Invention (Industrial Application Field) This invention is a tire mounted on the front idler axle of a vehicle such as a truck or bus, and in particular a tire that reduces the occurrence of uneven wear on its shoulder ribs. This relates to heavy-duty pneumatic tires.

(Prior Art) Radial tires, which have many characteristics such as excellent wear resistance and low rolling resistance, have recently become widely used in vehicles such as trucks and buses.

By the way, when such a tire is used as an idler wheel, local wear and tear occur before the tire wears out overall.
It is known that so-called uneven wear occurs, one of which is uneven wear in shoulder ribs formed near the ends of the tread by the circumferential main groove.

This is due to the difference in human force applied to the tires from the road surface.
This is because when minute wear occurs on the shoulder rib, the wear progresses at an accelerated rate as the tire is rotated due to the difference in diameter with respect to the tread surface of the tire.

In order to suppress the occurrence of such uneven wear on the shoulder ribs, in conventional tires, for example, as shown in FIG. A plurality of circumferential main grooves 12 are provided, and shoulder rib grooves 14 are provided near both ends of the tread portion and extend in the tire circumferential direction. It is proposed to define a shoulder rib 16 that is present.

Here, the shoulder rib grooves 14 are such that the ratio of the distance Rw from the tread end to the rib groove to l'' of the tire tread width, that is, the half width W of the tread, is approximately 6 to 25%. One end of the shoulder rib 16 is connected to the shoulder part +8.

When the tire is transferred, the said shoulder lift 1
By actively abrading the tread portion 6, other areas of the tread portion IO are uniformly abraded.

(Problem to be Solved by the Invention) However, when a conventional tire equipped with such shoulder rib grooves 14 is applied to a road having a relatively smooth road surface with many straight sections, it may not be possible to achieve the desired result. Although results can be obtained, when applied to a road with a rough road surface and many curved areas, it is easy to cause so-called shoulder drop wear on the shoulder rib I6, and the surface of the shoulder rib 16 is There are problems such as wave wear, which is uneven wear, and further problems such as tearing along the bottom of the shoulder rib groove 14.

The present invention has been made in view of such problems, and an object of the present invention is to provide a pneumatic tire in which the occurrence of uneven wear in the shoulder ribs is significantly reduced.

(Means for achieving the object) In order to achieve the object [1], the tire of the present invention has the following features:
In particular, the distance from the tire equatorial plane to the tread/sod end is W (w), the distance from the tread end to the shoulder rib groove is Rw (rm), and the groove width of the shoulder rib groove is Rs (w).
a), and when the groove depth is Rd (m), R, v/
W = 0.28~0.42, Rs/W = 0.05
~0.12, and Rd/W = Q, 37~0.1
9, and the angles α and β between the mutually opposing groove walls of the shoulder rib grooves and the line segment perpendicular to the tread surface are -'70≦α, β≦7. satisfies and becomes C.

(Function) According to this tire, by optimizing the groove position and groove wall angle of the shoulder rib groove, the rigidity of the shoulder rib can be made more appropriate, so that Uneven wear on the shoulder ribs can be effectively reduced not only on roads with many smooth surfaces, but also on roads with rough surfaces that have many curved areas.

(Embodiments) Preferred embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a preferred embodiment of the tire of the present invention. In this embodiment, the tread 20 has three main circumferential lines spaced apart from each other and extending in the tire circumferential direction. Groove 22;
Shoulder rib grooves 24 are provided near the tread ends apart from the circumferential main groove 22 in the tire width direction, and each of the shoulder rib grooves 24 has a shoulder rib 26 extending in the tire circumferential direction. define.

Further, at both ends of the tread 20, there are sipes 30 that extend in the tire width direction, are formed at predetermined intervals in the tire circumferential direction, and are continuous with the shoulder portion 28, and between the main grooves in the circumferential direction and ':l: A stepped inclined sipe 32 formed between the groove and the rib groove. The internal structure of the tire is a numerical radial structure, so
Illustration is omitted here.

The circumferential main groove 22 includes a straight line portion 22a extending substantially parallel to the equatorial plane of the tire, a short diagonal portion 22b diagonally connecting to this straight portion, and a short diagonal portion 22b diagonally intersecting this short diagonal portion. The tire includes a long diagonal portion 22c connected to the long diagonal portion, and another short diagonal portion 22d diagonally connected to the long diagonal portion and connected to another straight portion, which are alternately adjacent to each other in the tire circumferential direction. to form the circumferential main groove 22.

Similarly, the shoulder rib groove 24 defining the shoulder rib 26 also includes a straight part 24a extending substantially parallel to the equatorial plane of the tire, and a short diagonal part 24b obliquely connecting to this straight part. , a long diagonal portion 24c obliquely connected to this short diagonal portion, and another short diagonal portion 24d diagonally connected to this long diagonal portion and connected to another straight portion, and they are Rib grooves 24 are alternately formed adjacent to each other in the tire circumferential direction.

Therefore, including the shoulder rib 26, the circumferential main groove 22
The edge portions of the ribs extending in the circumferential direction of the tire defined by the shoulder rib grooves 24 and obliquely intersecting with the tire equatorial plane not only contribute to the driving performance and braking performance but also improve the tire performance. By resisting movement in the width direction, it is possible to suppress tire skidding and improve maneuverability and stability.

Moreover, when wet, the circumferential main grooves 22 and shoulder rib grooves 24 that extend in the circumferential direction of the tire not only ensure good drainage, but also ensure that these edge portions are free from water that forms on the road surface. It cuts the membrane and makes contact with the road surface, creating a so-called edge effect, which also improves wet performance.

What should be noted here is the arrangement of the shoulder rib grooves 24, and in the tire of the present invention, as shown in FIG. 2(a), the distance from the tire equatorial plane S to the tread edge 28, Distance R1 (
The ratio of W) is R, w/W = 0.28 to 0.42,
Preferably, it is selected to satisfy the relationship of 0.3 to 0.35.

The reason for choosing to satisfy such a relationship is that the distance W
When the distance Rw was variously changed and the percentage of tires in which uneven wear, particularly wave wear, occurred in the shoulder ribs 26 was investigated, the results shown in FIG. 2(b) were obtained.

As is clear from this figure, when the ratio of the rib width Rw of the shoulder rib 26 to the half width W of the tread exceeds 0.42 and the width exceeds 42%, the occurrence of wave wear becomes noticeable, and the shoulder rib A so-called step-down, in which the surface is completely worn, also occurs.

This is because when the ratio of the rib width to the tread half width exceeds 42%, the stiffness of the shoulder ribs 26 becomes too large compared to the stiffness of the center part of the tread 1/rad 20, which acts on the tire when the vehicle turns. This is because the ratio of the load to the side force becomes larger than that of the center portion of the tread 20, causing the shoulder ribs 26 to wear out. Then, due to the difference in tire diameter caused by this, wear progresses as the tire shifts, resulting in noticeable wave wear and further step-down.

On the other hand, when the ratio of the rib width RW to the tread width W becomes 0.28, that is, 28% or more, the stiffness of the shoulder ribs 26 becomes too small compared to the stiffness of the center part of the tread 20, causing problems. This is because the movement of the shoulder ribs 26 relative to the idle force increases, so that the wear rate of the shoulder ribs 26 becomes faster than that of the center part of the tread, causing uneven wear such as wave wear and step-down.

Therefore, it is preferable to select the ratio to be 30 to 35%.

The distance from the tread end 28 to the shoulder rib groove 24 is determined when the shoulder rib groove 24 extends in the circumferential direction while being bent in the width direction of the tire, as shown in FIG. C is, as shown in Figure 2(c),
This refers to the distance between the center of the amplitude d of the groove wall of the rib groove 24 located on the tread end 28 side and the tread end 28.

Although the ratio of the groove width Rs (am) of the shoulder rib groove 24 to the tread half width W is influenced to some extent by the groove width of the circumferential main groove, the ratio of the groove width Rs (am) of the shoulder rib groove 24 to the tread half width W is =0.05~0.12, and the groove depth Rd is Rd
It is assumed that the selection is made so as to satisfy the relationship: /W = 0.07 to 0.19.

Here, the groove width Rs of the shoulder rib groove 24 indicates the length in the tread width direction of the groove that opens on the tread surface of a new tire, and the groove depth Rd refers to the length from the tread surface to the groove bottom. It refers to the distance to.

Here, Rs/W = 0.05 to 0.12 is used when the ratio is 0.12, that is, when the shoulder rib groove width is larger than 12% with respect to the tread half width, the side force is applied. At the bottom, the side force acts relatively strongly at the rib end adjacent to the shoulder rib, so the machining/joint part of the rib is forced to wear, causing a difference in diameter, resulting in river wear, rib bunching, etc. On the other hand, if Rs/W is smaller than 5%, the stone-biting property deteriorates, and as a measure to improve this, it may be possible to arrange a stone protrusion, which will be described later, but the groove width Rs+ is too narrow and is not sufficient. This is because the groove bottom radius cannot be taken, and there is a concern about groove bottom tearing.

In addition, when Rs/W is close to zero, it is almost as if there is no shoulder rib groove, and the same problem will occur when the shoulder rib groove width is wide (Rw/W>0.42). Become.

On the other hand, when the ratio of the groove depth Rd of the shoulder rib groove 24 to the tread half width W, that is, Rd/W, becomes larger than 19%, the stiffness of the shoulder rib becomes relatively weak compared to that of other ribs. In particular, this is because the movement of the shoulder ribs in response to the side force input becomes thicker (as a result, the wear rate increases, so the step-down becomes more pronounced. On the other hand, if Rd/W is less than 7%, the shoulder ribs will move more quickly in response to the side force input). Since the groove disappears and the apparent width of the shoulder rib increases from then on, the stiffness of the shoulder rib becomes too large compared to the tire center groove.
This is because the burden on the side force becomes larger than that of the central rib, and the shoulder part wears out, and the resulting difference in diameter causes wave wear and step-down to become noticeable. Therefore, the ratio Rd/W of groove depth to tread half width is 7 to 19%,
Preferably it is in the range of 12 to 16%.

Furthermore, as shown in FIG. 3(a), the angle α between the normal N to the surface of the tread portion 20 and the mutually opposing groove walls M, , M of the shoulder rib groove 24, β
is selected so as to satisfy the relationships −7°≦α and β≦−7°.

This is, for example, a groove wall M located on the center side of the tread portion 20, as schematically shown in FIG.

When the angle β between the groove wall and the normal N to the tread surface takes a relatively large value, the stiffness at the intersection between the groove wall and the tread becomes higher than the stiffness at the opposing shoulder rib 26. This is because, while the edges at the intersection are worn, a step-down occurs in the shoulder rib 26.

On the other hand, as shown in FIG.
When the angle α between the shoulder rib 26 and the shoulder rib 26 is increased to increase the rigidity of the shoulder rib 26 against side force, the wear rate of the rib becomes faster than that of the adjacent rib, that is, the rib located closer to the center of the tread. This is because the step-down in the shoulder rib 26 becomes noticeable.

Therefore, in the present invention, the occurrence of uneven wear in the shoulder ribs 26 was investigated by variously changing the angles formed by the respective groove walls M and %M with respect to the normal N to the tread surface. It is preferable that the angles α and β are −7° or more and 7° or less (preferably,
As shown in FIG. 3(a), it was found that a range of 06 to 4 degrees gave good results.

By the way, as is clear from FIG. 3(a), the tire of the present example has a higher resistance to the tread surface of the groove walls M1, M of the shoulder rib groove 24 than the conventional tire. Since the angle at which it is made is small, there is a risk of what is called a stone-biting problem.

Therefore, in this embodiment, FIGS. 1 and 2(a)
As is clear from the figure, stone protrusions 32 are provided within the shoulder rib groove 24 at predetermined intervals in the direction in which it extends. The protruding end surfaces of these protrusions 32 are connected to the tread portion 2
It is located radially inward of the tire from the surface of the tire, and when the tread portion 20 comes into contact with the road surface, stones, etc. that are pushed into the shoulder rib groove 24 against the stone protrusion 32 are removed. In areas freed from contact with the road surface,
It is pushed out by the elastic restoring force of the stone protrusion 32.

Furthermore, in this example, similar stone protrusions were also provided in the circumferential main groove provided along the tire's equatorial plane, but this is not limiting. In addition to being disposed in the circumferential main groove of the groove, the stone protrusions are not necessarily disposed in the shoulder rib groove or the circumferential main groove.

1 Comparative Example] Hereinafter, a comparative test regarding the uneven wear performance of the tire according to the present invention and a conventional tire will be described.

() Test Tire Tire size is a tire with a radial structure of It R22,5/+6PR Invention Tire A tire with a tread pattern shown in Figure 1, tread width 210 mm, circumferential main groove width 11.5 m, circumference Directional main groove center spacing 32.5 m, circumferential main groove depth 13.7 m, shoulder rib groove position (distance from tread end) 34.
1m, Sicolder rib groove groove width 8.8mm, Shoulder rib groove groove depth 15.2n+s, Sipe circumferential pitch 7.1
1.

・Conventional Tire A tire with a tread pattern shown in Figure 4, with a shoulder rib groove position (distance from the tread edge) of 521.
! What I did.

◎The tires described in the test method were mounted on the front idler axle of the same vehicle, and the vehicles were driven in each test area, and the distance traveled until tire replacement due to uneven wear was compared.

◎Test results The test results are shown in the table below.

Table 1 Table 2 Table 3 (Test Driving Area C) According to the list, the tires of the present invention were used in all regions until the tire was replaced due to uneven wear in the shoulder blocks of the tire. It is clear that the mileage of the tires can be extended compared to conventional tires.

Note that the present invention is not limited to the embodiments described in -1-, and the shoulder rib grooves may extend substantially parallel to the tire equatorial plane, and various modifications may be made within the scope of the claims. can be added.

(Effects of the Invention) Thus, according to the present invention, uneven wear on the shoulder ribs of the tire can be effectively prevented, as shown in the above tables.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the tire of the present invention, and FIG. 2 (
a) is a cross-sectional view taken along line A-A in FIG. 1; FIG. 2(b) is a cross-sectional view showing the shoulder rib width relative to the tread half width of the tire;
FIG. 2(C) is a diagram showing the groove amplitude of the shoulder rib groove forming the shoulder rib. FIG. 3(a) is a diagram showing the relationship with uneven wear in the shoulder rib. FIG. Figures 3(1) and 3(c) are diagrams showing the cross-sectional shape of the shoulder rib groove, respectively, and Figure 4 is a diagram showing the relationship between the cross-sectional shape of the shoulder rib groove and uneven wear of the shoulder rib. FIG. 10, 20...Tread 12.22...Circumferential 1-mo groove 14, 24...Shoulder rib groove 16, 26...Shoulder rib 18, 28...Sikorda part 30.32...Sipe 32...Stone protrusion patent applicant Brideston Co., Ltd. Patent attorney Akatsuki Sugimura Examiner Patent attorney
Figure 2 (a) (b) (Shiman) Figure 3 (a) (b) (C) by Ko Sugimura

Claims (1)

[Scope of Claims] 1. At least one circumferential main groove extending in the circumferential direction of the tread portion of the tire, and at least one circumferential main groove formed near the tread end at a distance from each other in the circumferential main groove. In a heavy-duty pneumatic tire that is provided with shoulder rib grooves that define shoulder ribs, the distance from the tire equatorial plane to the tread edge is W (mm).
, the distance from the tread end to the shoulder rib groove is Rw
(mm), the groove width of the shoulder rib groove is Rs (mm), and the groove depth is Rd (mm), Rw/W=0.28~0.42, Rs/W=0.05~0 .12 Satisfying the relationship Rd/W=0.07 to 0.19, the mutually opposing groove walls of the shoulder rib groove,
A pneumatic tire for heavy loads, characterized in that angles α and β formed with a line segment perpendicular to the surface of a tread portion satisfy the following relationships: −7°≦α, β≦7. 2. The heavy-duty air compressor according to claim 1, wherein the shoulder rib grooves are provided with stone protrusions extending spaced apart from each other in the tire circumferential direction and located radially inward of the tire from the tread surface. Included tires.